Promiscuous Lipase-Catalyzed Knoevenagel-Phospha-Michael Reaction for the Synthesis of Antimicrobial β-Phosphono Malonates

An enzymatic route for phosphorous-carbon bond formation was developed by discovering new promiscuous activity of lipase. We reported a new metal-free biocatalytic method for the synthesis of pharmacologically relevant beta-phosphonomalononitriles via a lipase-catalyzed one-pot Knoevenagel-phospha-Michael reaction. We carefully analyzed the best conditions for the given reaction: the type of enzyme, temperature, and type of solvent. A series of target compounds was synthesized, with yields ranging from 43% to 93% by enzymatic reaction with Candida cylindracea (CcL) lipase as recyclable and, a few times, reusable catalyst. The advantages of this protocol are excellent yields, mild reaction conditions, low costs, and sustainability. The applicability of the same catalyst in the synthesis of beta-phosphononitriles is also described. Further, the obtained compounds were validated as new potential antimicrobial agents with characteristic E. coli bacterial strains. The pivotal role of such a group of phosphonate derivatives on inhibitory activity against selected pathogenic E. coli strains was revealed. The observed results are especially important in the case of the increasing resistance of bacteria to various drugs and antibiotics. The impact of the beta-phosphono malonate chemical structure on antimicrobial activity was demonstrated. The crucial role of the substituents attached to the aromatic ring on the inhibitory action against selected pathogenic E. coli strains was revealed. Among tested compounds, four beta-phosphonate derivatives showed an antimicrobial activity profile similar to that obtained with currently used antibiotics such as ciprofloxacin, bleomycin, and cloxacillin. In addition, the obtained compounds constitute a convenient platform for further chemical functionalization, allowing for a convenient change in their biological activity profile. It should also be noted that the cost of the compounds obtained is low, which may be an attractive alternative to the currently used antimicrobial agents. The observed results are especially important because of the increasing resistance of bacteria to various drugs and antibiotics.